1. Field of the Invention
The present invention relates to a control unit of an image forming device for printing images based on print data, and more specifically to a control unit including a memory for storing print data even after the images are printed out.
2. Description of Related Art
There has been provided a system including a plurality of personal computers and a printer communicable with each other via a local area network (LAN) including a host computer. This kind of system is being used in an increasing number of companies. Because, in this kind of system, users of the personal computers can share a single printer, costs of office equipment can be reduced, and also space taken up by the equipment in the office can be saved.
However, In this case, some personal computers may be located a fair distance from the printer. When a user of such personal computer wishes to print out a document, the user operates an input unit of the personal computer to transmit print data to the printer, and then, walks to the printer to fetch the document. After the user examines and approves contents of the document, the user may wish to obtain additional copies of the document. In this case, the user needs to walk back to the personal computer to again transmit the print data to the printer.
There has been also proposed an image forming device including a memory for storing print data transmitted from an external device. The print data is stored in the memory without being erased at least until an image is formed based on the print data.
When this kind of printer is provided in the above described system, the same image can be repeatedly formed as long as the print data is stored in the memory. Therefore, the user needs not walk back to the personal computer to again transit the print data when the user wishes to obtain the additional copies of the document.
However, when an other user transmits different print data to the printer, the current print data in the memory is replaced by the different print data. That is, the current print data may be erased while the user is examining the contents of the document. Then, when the user wishes to obtain additional copies of the document, the user needs to go back to the personal computer to again transmit the print data.
It is conceivable to print out a plurality of copies of the document from the beginning without examining the contents of the document. However, in this case, if the user finds errors in the contents, all copies will need to be disposed. This means that the user wastes time for printing out copies of flawed and undesirable document. Also, the recording media used for these copies is also wasted.